1. Field of the Invention
The invention relates to grand pianos and more particularly to such means whereby key touch resistance can be adjustably controlled by a device, efficiently installed within the limited space of the grand piano cabinetry. without permanently altering its original components .
2. Description of the Prior Art
Virtually all musical keyboard instruments have a conventional arrangement of keys which, when depressed, produce musical sounds. In the case of acoustic pianos, keys are typically pivotally mounted levers which transfer an input finger force into the piano action assembly. The design orientation of acoustic pianos can be either vertical, as in the case of upright pianos, or horizontal as with grand pianos. Even within the finest piano actions, substantial mass, inertia, spring and friction forces are present and must be carefully adjusted for balance and consistency, creating a tactile characteristic known as “touch weight” within the keyboard . When pianos age, this touch weight can degrade due to rising levels of friction and misalignment among the rotating and sliding components of the action. This touch weight increase can also occur when worn components within the action are replaced with new parts which are heavier than the original parts. The touch weight increase can produce an unpleasant sense of heaviness and slow key acceleration. It can also degrade unevenly between the keys resulting in inconsistent action response. This tendency toward heavy touch weight is especially prevalent in grand pianos which have horizontally oriented action mechanisms which must rotate upward against the force of gravity. The only conventional remedy for this problem, beyond the scope of routine adjustment and lubrication, is the removal addition or relocation of existing mass loading components such as the lead ballast weights which are This process of action weight adjustment is a specialized art. Recent examples are taught by Davide (U.S. Pat. No. 6,096,959), Inoue (U.S. Pat. No. 7,129,404 B2), Ito et. al. (U.S. Pat. No. 4,686,879) and Kugimoto et. al. (U.S. Pat. No. 6,774,294, B2). Additionally, numerous mechanical devices for the control of grand piano action touch weight have been created. Typically, these devices apply various forces of either gravitational, mechanical or electro-magnetic origin to the piano keys. Examples of these devices are instructed by Conklin Jr. et. al.(U.S. Pat. No. 4,381,691) Inoue (U.S. Pat. No. 6,649,821 B2) and Gunther (U.S. Pat. No. 2,911,874). Such devices can be difficult to adjust because their location within the piano is not easily accessible. The devices can be costly to manufacture and can require significant modification to the existing piano. The devices can be difficult to remove, hindering conventional service access to other regions of the action.
When grand pianos are transported, they must be tilted and rotated in order to move the instrument through small openings such as doorways and stairwells. This tilting process can easily dislodge the keys from the action, resulting in damage to the keys, action or cabinetry. To prevent this, grand piano actions are equipped with a key stop rail, made of wood or metal, rigidly suspended above and in close proximity to the key upper surfaces. The key stop rail is strategically positioned to limit excessive upper movement of the keys while not interfering with moving cabinet panels or blocking access to adjustment points within the action. Also, the key stop rail is easily removable, facilitating adjustment and service of the keys.